Cara Nelson (above) was one of 51 runners to embark on this year's World Marathon Challenge, which included runs in Novo, Antarctica (left), and Perth, Australia.World Marathon Challenge

Cara Nelson ran her first marathon a little over year ago — and never looked back.

On Monday, Feb. 5, the East Hampton Middle School social-studies teacher crossed the finish line of her seventh marathon in seven days, run on each of the seven continents.

She was taking part in the fourth annual World Marathon Challenge, a series of 26.2-mile races run in Antarctica, South Africa, Australia, United Arab Emirates, Portugal, Colombia and the US, all completed within a week.

“I had no idea what to expect,” Nelson, 31, tells The Post.

The challenge is organized by the Isle of Man-based Global Running Adventures organization, and this year’s event included 51 runners from around the world, competing individually and in groups. The race cost around 36,000 euros per person, although Nelson’s team’s expenses were covered by an anonymous donor, and any and all money raised went to charity.

Nelson, who was born in Smithtown, LI and lives in Moriches, LI, was one of 16 American runners grouped together under the name Team Hold the Plane. She and her husband, Chris, were on their honeymoon in Peru in 2015 when they met the group’s leader, David Samson, who told them about his dream of building a team for the then-brand-new challenge. The two kept in touch, even though Nelson thought it seemed pretty far-fetched.

Nelson hits the streets of Miami.World Marathon Challenge

To get ready for the feat, which kicked off in Antarctica on Jan. 30, she trained for 18 months. She ran dozens of miles each week, participated in a handful of marathons and practiced yoga, fitting her workouts in between teaching and coaching soccer, basketball and lacrosse. She prepared as well as she could, then hoped for the best.

“It ended up being mentally taxing,” says Nelson. “My body surprised me in how well it did.” She stayed limber by foam-rolling on the team’s chartered jet, and sleeping as they flew from continent to continent.

“At a few of the locations, there [was] time for a five-hour stay, to get a few hours sleep and get a nice warm shower, but not at all of them,” says Nelson. “We’d get off the plane, go through customs, have 15 minutes to get ready, go run, have a few hours to relax, then go back to the hotel, grab our bags, and get right back on the plane to repeat the process.

Her feet blistered, her toes swelled and her skin burned under the Australian and South African sun. In Colombia, shoddy trail mapping meant her team was never sure when it would reach the finish line — an experience that left Nelson questioning whether she could complete the race.

‘What I wanted my kids to take away was, ‘You’re always going to encounter struggles and obstacles, and you have to push through.’

Still, Nelson says the challenge was life-changing.

“I realized that as long as you put mind over matter, you can really accomplish everything you want out of life,” she says. It’s a message she hopes to pass along to her young students. “What I wanted my kids to take away was, ‘You’re always going to encounter struggles and obstacles, and you have to push through.’”

As she raced around the world, her students were kept busy. Nelson used Google Classroom to create a presentation, video and series of assignments for each race location, which the students completed with a substitute teacher.

“[My students looked] into the seven cities I’m running in, and [looked] at how geography impacts my run,” Nelson says. And between races, she held Skype sessions to check in and answer questions. When she returned to class less than 48 hours after crossing the finish line in Miami, they greeted her with hugs, high-fives and World Marathon Challenge T-shirts.

She said her students’ enthusiasm and support kept her going — as did her teammates.

“One of the most surprising things about the trip was the camaraderie,” she says. “The sport of racing is always about your own individual achievement. But in every single race, it was so beautiful to see how we were cheering everybody on and slowing down to finish with teammates. We were just running to get everybody across the finish line.”

Cara Nelson

Issa Saleh Alkindy

Nelson is given a sendoff at East Hampton Middle School before the World Marathon Challenge.

Gordon M. Grant

Nelson gets a hug from fellow teacher Lea Bryant during her sendoff.

Gordon M. Grant

Nelson (#20) makes tracks during the Africa Intercontinental Marathon in South Africa.

World Marathon Challenge

In Novo, Antarctica, Nelson (center) poses with the banner of support from East Hampton Middle School, where she teaches.

World Marathon Challenge

Nelson (second from right) runs in the Antarctica Intercontinental Marathon.

World Marathon Challenge/Rodolfo Soto

Nelson runs in Cartagena in Colombia.

Provided by Cara Nelson

Nelson is accompanied by other runners in Miami.

World Marathon Challenge

Nelson shows off her medals in Miami.

World Marathon Challenge

World Marathon Challenge

Nelson talks with her class after completing the seven-marathon challenge.

Gordon M. Grant

Nelson is given a present by seventh-grader Olivia Masone, 12, upon her return.